Patterned overcoat layer

ABSTRACT

A composite article includes a conductive layer on at least a portion of a flexible substrate, wherein the conductive layer has a conductive surface. A patterned layer of a low surface energy material is on a first region of the conductive surface. An overcoat layer free of conductive particulates is on a first portion of a second region of the conductive surface unoccupied by the patterned layer. A via is in a second portion of the second region of the conductive surface between an edge of the patterned layer of the low surface energy material and the overcoat layer. A conductive material is in the via to provide an electrical connection to the conductive surface.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage filing under 35 U.S.C. 371 ofPCT/US2016/039024, filed Jun. 23, 2016, which claims the benefit of U.S.Application No. 62/187,192, filed Jun. 30, 2015, the disclosure of whichis incorporated by reference in its/their entirety herein.

BACKGROUND

Transparent conductors are utilized on touch screens to enable humantouch or gesture interactions with computers, smart phones, and othergraphics-based screen interfaces. Touch screen devices can be made bypatterning (e.g., printing) a conductive material into electrical traceson a flexible substrate. Patterning of the conductive material can beperformed in a roll-to-roll process where the substrate is unwound,converting operations such as printing and drying/curing are performed,and then the patterned substrate is wound again into a roll for furthertransport and processing. The patterned conductive layers can beconnected to electronic circuit components such as, for example,flexible circuits, to form an electronic touch sensor that can be usedas a component of an electronic device.

There are several approaches to patterning the conductive materials foruse in electronic assemblies such as, for example, touch sensors.

In one example, the conductive material can be printed directly to forma pattern from a dispersion or ink, using standard printing processessuch as, for example, ink-jet, gravure, flexographic, or screenprinting. This direct printing technique produces a pattern in one step,with minimal waste. However, variations in the print thickness due todefects such as ribbing and pinholes may produce unacceptable variationsin conductivity, as well as negatively impacting the optics of thesensor.

In another example, the surface of the substrate can be uniformly coatedwith the conductive material by forming a substantially continuousconductive layer. A resist material is then printed on the conductivelayer using printing processes such as, for example, flexographicprinting, gravure printing, ink jet printing, screen printing, spraycoating, needle coating, photolithographic patterning, and offsetprinting. The patterned resist material allows selective removal ofportions of the conductive layer to create a desired pattern(subtractive patterning). Selective removal is often accomplished eitherby wet chemical etching or laser ablation.

In some manufacturing processes, patterns of material may be depositedon the flexible substrate in layers through multiple deposition steps.Some articles require that the patterns be precisely registered on oneor both sides of the substrate. To achieve accurate registration betweenthe layers, lateral (cross web) positioning and longitudinal (down web)positioning must be maintained as the substrate moves through multiplemanufacturing steps. Maintaining registration between layers formed onthe substrate becomes more complex when the substrate is flexible orstretchable, and the patterns are made smaller and more intricatelydetailed. Various methods have been employed to improve the accuracy ofthese registration steps such as, for example, edge detection and theprinting of fiducial marks.

In some fabrication processes, layers of conductive material arepatterned, with each patterned layer separated by an insulatingmaterial. To make electrical connections to and between the conductivepatterned layers in such a multi-layer construction without formingshort-circuits, it can be important to create and maintain a reliableconductive path, generally referred to as a via, between thenon-adjacent patterned conductive patterned layers. However, preciseregistration between adjacent layers to form vias in a multi-layerconstruction can be difficult, time-consuming and expensive.

SUMMARY

To reliably manufacture electronic touch screen devices in aroll-to-roll process using printing processes such as, for exampleink-jet, gravure, flexographic, or screen printing, reliable techniquesfor forming vias between non-adjacent conductive layers can reducedefects and lower product costs.

In general, the present disclosure relates to a self-forming via thatcan be easily created and reliably maintained during the application andregistration of multiple printed conductive layers separated byinsulating layers. In the method a patterned layer of a low surfaceenergy material is formed in a first region of the conductive surface,with a second region remaining uncoated by the patterned layer. When alayer of a liquid overcoat composition is coated over the first and thesecond regions, the difference in the wettability of the first regionrelative to that of the second region destabilizes the layer of theliquid overcoat composition and causes the liquid overcoat compositionto dewet from the low surface energy material and withdraw from thepatterned layer. A first amount of the liquid overcoat compositionrecedes from the edges of the patterned layer and a collects in a firstportion of the second region of the conductive surface. A secondresidual amount, which is smaller than the first amount, remains in asecond portion of the second region of the conductive surface adjacentto the edges of the patterned. When the liquid overcoat composition iscured to form an overcoat layer, a via created in the second portion ofthe second region of the conductive surface can be utilized as an accesspoint to form an electrical connection to the conductive surface. Usingthe via, an electrical connection can be formed with the conductivesurface by various techniques such as, for example, applying aconductive paste in the via, or by directly bonding an electronicconnection to the conductive surface in the via.

In some embodiments, the overcoat layer can act as a further substrateonto which another low surface energy pattern can be created and afurther overcoat solution coated, or the overcoat layer can be removedas necessary. Third and subsequent patterned layers can be formed byrepeating a similar surface wettability modification technique, but thevia formed on the conductive surface by the initial low surface energypattern remains in registration as the additional layers are added, andcontinues to provide a reliable path for electrical connection to theconductive surface.

In one aspect, the present disclosure is directed to a composite articleincluding a conductive layer on at least a portion of a flexiblesubstrate, wherein the conductive layer has a conductive surface. Apatterned layer of a low surface energy material is on a first region ofthe conductive surface. An overcoat layer free of conductive particlesis on a first portion of a second region of the conductive surfaceunoccupied by the patterned layer. A via is in a second portion of thesecond region of the conductive surface between an edge of the patternedlayer of the low surface energy material and the overcoat layer, and aconductive material in the via provides an electrical connection to theconductive surface.

In another aspect, the present disclosure is directed to a compositearticle including a conductive layer on at least a portion of a flexiblesubstrate, wherein the conductive layer has a conductive surface. Apatterned conductive layer is on a first region of the conductivesurface, wherein a second region of the conductive surface is uncoveredby the patterned conductive layer. A patterned low surface energy layeris on a first portion of the patterned conductive layer, wherein asecond portion of the patterned conductive layer is uncovered by thepatterned low surface energy layer. An overcoat layer free of conductiveparticulates is on the second region of the conductive surface, and avia is between the overcoat layer and first portion of the patternedconductive layer, wherein the via overlies the second portion of thepatterned conductive layer. A conductive material in the via provides anelectrical connection to the patterned conductive layer and theconductive surface.

In another aspect, the present disclosure is directed to a method offorming a composite article, including: coating a patterned layercomprising a low surface energy material onto a first region of aconductive surface disposed on a flexible substrate, wherein a secondregion of the conductive surface remains uncovered by the patternedlayer; coating a layer of a liquid overcoat composition over thepatterned layer of the low energy material and the second regions of theconductive surface, wherein the liquid overcoat composition has asurface energy different from the surface energy of the low surfaceenergy material; de-wetting the liquid overcoat composition from thepatterned layer of the low surface energy material such that the liquidovercoat composition withdraws from the patterned layer of the lowsurface energy material and a first amount of the liquid overcoatcomposition collects in a first portion of the second region of theconductive surface, wherein the liquid overcoat composition recedes froman edge of the patterned layer of the low surface energy material suchthat a second residual amount of the liquid overcoat composition lessthan the first amount remains in a second portion of the second regionof the conductive surface adjacent to the edge of the patterned layer ofthe low surface energy material; curing the liquid overcoat compositionto form a discontinuous overcoat layer in the first portion of thesecond region of the conductive surface and a via in the second portionof the second region of the conductive surface, wherein the via isadjacent to the edge of the patterned layer of the low surface energymaterial; and electrically contacting the conductive surface through thevia.

In yet another aspect, the present disclosure is directed to a method offorming a composite article, including: coating a first patterned layerof a conductive material on a first region of a conductive surface on aconductive layer disposed on a flexible substrate, wherein a secondregion of the conductive surface is uncoated by the first patternedlayer of the conductive material; coating a second patterned layer of alow surface energy material on a first portion of the first patternedlayer of the conductive material, wherein a second portion of the firstpatterned layer is uncoated by the second patterned layer; coating alayer of a liquid overcoat composition onto the first and the secondregions of the conductive surface, wherein the liquid overcoatcomposition has a surface energy greater than the surface energy of thelow surface energy material in the second patterned layer; de-wettingthe liquid overcoat composition from the second patterned layer of thelow surface energy material such that a first amount of the liquidovercoat composition withdraws from the second patterned layer andcollects in the second region of the conductive surface, and wherein asecond amount of the liquid overcoat composition less than the firstamount remains in the second portion of the first patterned layer of theconductive material; curing the liquid overcoat composition to form adiscontinuous overcoat layer in the second region of the conductivesurface, wherein the overcoat layer is separated from the secondpatterned layer by a via overlying the second portion of the firstpatterned layer; and electrically contacting the second portion of thefirst patterned layer through the via.

The methods described in this disclosure can enable roll-to-rollcontinuous patterned coating, which has significant cost andproductivity benefits over batch processes. As only desired areas on theconductive surface are coated with the overcoat solution, the presentlydescribed method can more cost-effectively use coating materials. Invarious embodiments, the techniques of the present disclosure can beused for low-cost manufacture of, for example, flexible displays,electronics, OLED's, PLEDs, touch-screens, fuel-cells, solid statelighting, photovoltaic and other complex opto-electronic devices.

In various embodiments, the present method provides a number ofadvantages over techniques in which the liquid overcoat composition isprinted directly on the conductive surface, particularly in high-speedcontinuous roll-to-roll processes. For example, rotary printingprocesses (such as flexography, gravure, and rotary screen printing)transfer a liquid from one roll to the next, which is known as a filmsplit. This film split can result in a ribbing defect, which producesnon-uniformities in the coating. By applying the liquid overcoatcomposition as a continuous layer, instead of as a pattern, coatingmethods can be used that do not require a film split, such as diecoating, notch bar coating, or reverse gravure coating. The technique ofthe present disclosure can also allow more precise control of thethickness of the liquid overcoat composition. More precise control ofcoating thickness can reduce non-uniformities produced by the ribbingdefect and reduce the formation of pinholes in the overcoat layer, whichprovide unwanted access points to areas of the underlying conductivelayer. Removing the necessity of printing the liquid overcoat layer canalso increase the number of different materials available for use asovercoats, since the restrictions on the rheology of a printed materialcan be much greater than on a coated material.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A-1E are schematic cross-sectional views of an embodiment of aprocess for making an overcoat layer on a conductive surface and makingan electrical connection to the conductive surface.

FIG. 1C-1 is a magnified cross-sectional view of an embodiment of aprocess for making an overcoat layer on a conductive surface and makingan electrical connection to the conductive surface.

FIGS. 2A-2E are schematic cross-sectional views of another embodiment ofa process for making an overcoat layer on a conductive surface andmaking an electrical connection to the conductive surface.

FIG. 3 is a schematic, cross-sectional view of a touch-screen display.

FIG. 4A is a photograph of a regular array of 500 μm pitch lines printedon a silver nanowire coating according to the procedure in Example 1.

FIG. 4B is a photograph of another printed pattern produced according toExample 1, which represents the opening of a contact pad (e.g. thecontact pad of a silver interconnect pattern), for which the squareopening is approximately 2 mm on each side.

FIG. 5A is a photograph of a regular array of 500 μm pitch lines pastedon top of a patterned overcoat layer produced according to the procedurein Example 1.

FIG. 5B is a photograph demonstrating that the silver pitch lines makecontact with the underlying nanowire conductive layer in the gapsbetween the dewetted over-coating layer and the low surface-energysilicone print features.

FIG. 6 is a photograph of a pad of a printed silver interconnect layermade according to the procedure of Example 2.

Like symbols in the drawings indicate like elements.

DETAILED DESCRIPTION

The present disclosure describes processes for coating discrete areas ofa flexible substrate in a continuous roll-to-roll manner. In general,the methods include creating a pattern of a low surface energy materialin a first region of a conductive surface, which leaves relativelyhigher surface energy second regions of the conductive surface uncoated.When an overcoat solution is coated on the first and the second regions,the overcoat solution dewets and withdraws from the first region of theconductive surface, and recedes from the edges of the low surface energypattern. A first amount of the overcoat solution collects in a firstportion of the second region. A second residual amount of the overcoatsolution, which is less than the first amount, remains in a secondportion of the second region adjacent to the edges of the low surfaceenergy pattern, and can provide a path to access the conductive surface.

Referring to an embodiment of the process illustrated schematically inFIG. 1A, a conductive layer 22 is disposed on a flexible substrate 20.The flexible substrate 20 can be clear or opaque, conductive ornon-conductive (insulative), and suitable flexible substrates can beselected from any material that can be rolled up and processed in aroll-to-roll manufacturing process. Examples of suitable flexiblesubstrates 20 include, but are not limited to: polyesters (e.g.,polyethylene terephthalate (PET), polyester naphthalate (PEN), andpolycarbonate (PC)), polyolefins (e.g., linear, branched, and cyclicpolyolefins), polyvinyls (e.g., polyvinyl chloride, polyvinylidenechloride, polyvinyl acetals, polystyrene, polyacrylates, and the like),cellulose ester bases (e.g., cellulose triacetate, cellulose acetate),polysulphones such as polyethersulphone, polyimides, silicones and otherconventional polymeric films. Additional examples of suitable substratescan be found in, e.g., U.S. Pat. No. 6,975,067.

Optionally, a major surface 21 of the substrate 20 underlying theconductive layer 22 can be pre-treated to prepare the surface to betterreceive the subsequent deposition of the conductive layer. In someembodiments, the pre-treatment step can be carried out in conjunctionwith a patterning step to create patterned deposition of the conductivelayer 22. For example, pre-treatments can include solvent or chemicalwashing, heating, deposition of an optional patterned intermediatelayer, as well as further surface treatments such as plasma treatment,ultraviolet radiation (UV)-ozone treatment, or corona discharge.

The conductive layer 22 can be applied to the substrate 20 at a giventhickness selected to achieve desired optical and electrical properties.This application can be performed using known coating methods, such as,for example, slot coating, roll coating, Mayer rod coating, dip coating,curtain coating, slide coating, knife coating, gravure coating, notchbar coating or spraying, yielding a conductive nanowire layer on thesubstrate. The conductive layer 22 can also be depositednon-continuously using a printing technique including, but not limitedto, gravure, flexographic, screen, letterpress, ink-jet printing, andthe like.

Suitable materials for the conductive layer 22 include, but are notlimited to, layers of metals or metal alloys of Cu, Ag, Au and the like,indium tin oxide (ITO), or layers of conductive metal or non-metallicfilaments, fibers, rods, strings, strands, whiskers, or ribbons in asuitable binder. Examples of non-metallic conductive materials for theconductive layer 22 include, but are not limited to, carbon nanotubes(CNTs), metal oxides (e.g., vanadium pentoxide), metalloids (e.g.,silicon), conductive polymer fibers, and the like.

The conductive layer 22 is substantially continuous over at least aportion of the first major surface 21 of the flexible substrate 20, anddesirably over at least 50%, 60%, 70%, 80%, or 90% of the area of thefirst major surface 21. The conductive layer 22 may be coatedcontinuously along the surface 21 of the flexible substrate 20, or maybe applied in discrete blocks or rectangles, leaving uncoated substrateareas between them, with the blocks or rectangles having a size similarto the overall size of the intended touch sensor being produced. By“substantially continuous” it is meant the conductive layer 22 isapplied at a sufficient density to render the surface 21 of thesubstrate 22 conductive, it being recognized that the surface 21 mayinclude individual conductive areas with relatively non-conductiveopenings or spaces between them.

Referring again to FIG. 1A, a pattern 24 of a low surface energymaterial is coated on and overlies a first region 50 of a conductivesurface 23 the conductive layer 22, which leaves a second relativelyhigher surface energy region 52 of the conductive surface 23 uncoated.In this application the term low surface energy material refers to anymaterial (for example, an ink) that can induce dewetting of asubsequently applied overcoat composition in a desired area of thesurface 23 of the conductive layer 22. Suitable low surface energymaterials for the pattern 24 can vary widely, and can include, but arenot limited to plastics, rubbers and composite materials with a surfaceenergy of less than about 100 mJ/m², less than about 50 mJ/m², less thanabout 30 mJ/m², less than about 20 mJ/m², or less than about 10 mJ/m².Non-limiting examples of low surface energy materials includefluoropolymers such as polyhexafluoropropylene, polytetrafluoroethylene(PTFE) and the like, was well as polymeric resins such aspoly(vinylidene fluoride) (PVF), polyethylene (PE), polypropylene (PP),poly(methylmethacrylate) (PMMA), polystyrene (PS), polyamides,poly(vinylchloride) (PVC), poly(vinylidene chloride), poly(ethyleneterephthalate) (PET), epoxies, phenol resins, styrene-butadiene rubber,acrylonitrile rubbers, and the like, thermally curable or ultraviolet(UV) curable silicones, and mixtures and combinations thereof. In someembodiments, the low surface energy material included silicones such asthose available from Dow Chemical, Midland, Mich., under the tradedesignation Syl-Off.

The coating composition used to form the pattern 24 typically includesat least one of the low surface energy materials listed above andoptional additives such as a fluorinated or non-fluorinated surfactant,a crosslinker, an aqueous or organic solvent, and the like. In someexample embodiments, the coating solution used to form the pattern 24includes a low surface energy material such as a thermally or UV curablesilicone “ink” and a crosslinker, or an acrylic resin and a fluorinatedsurfactant. In some embodiments, the coating composition used to formthe pattern 24 may be combined with a conductive material such as, forexample, metal particles or a silver paste ink, to make the pattern 24of the low surface energy material itself be conductive and provideadditional points of access to the conductive surface 23 of theconductive layer 22.

The coating composition used to form the pattern 24 may be coated on theconductive surface 22 by a wide variety of printing techniques such as,for example, flexographic printing, gravure coating, offset printing,screen printing, plasma deposition, photolithography, micro-contactprinting, inkjet printing or selective removal of a uniform layer of thematerial by laser or other etching technique, optically writing withlight or a laser, electrostatic spray or by plasma treatment.

In various embodiments, the patterned layer 24 of the low energymaterial has a dry thickness of about 100 nm to about 10 μm.

Referring to FIG. 1B, a liquid overcoat composition 25 is then coatedover the conductive surface 23 of the conductive layer 22, and initiallycovers both the printed pattern of the low surface energy material 24overlying the first region 50 of the surface 23, as well as the secondregion of the surface 23 that is uncoated with the pattern 24. Invarious embodiments, the liquid overcoat composition is coated to athickness of about 10 μm to about 15 μm. The liquid overcoat composition25 may be applied to the conductive surface 23 using any suitableprinting technique including, for example, flood coating, gravurecoating, curtain coating, bead coating, offset printing, screenprinting, inkjet printing, spraying, or by means of a blade, roller, orair knife.

The liquid overcoat composition 25 can include any material having asurface energy sufficiently greater than that of the low surface energymaterial in the pattern 24 to cause the liquid overcoat composition todewet from the pattern 24 in a commercially useful amount of time. Thespeed at which the liquid overcoat composition 25 rearranges about thepatterned layer 24 can impact the speed at which the predetermined areasof the conductive surface 23 can be coated in a roll-to-roll process. Adiscussion of the rates of recession of liquids from low surface energymaterials can be found in, for example, Brouchard-Wyart and de Gennes,Advan. Colloid Interface Sci., 39 (1992), which is incorporated hereinby reference.

If the liquid coating composition 25 is coated as a uniform layer, it isnecessary to destabilize the layer so the liquid overcoat compositionseparates, flows off, and withdraws from the patterned layer 24 of thelow surface energy material. While not wishing to be bound by anytheory, presently available evidence indicates that if the liquidovercoat composition 25 is sufficiently dilute, or when it becomessufficiently thin during subsequent drying steps, spontaneous dewettingfrom the pattern 24 to the regions 52 of the conductive surface 23 areastakes place, without the need for any active destabilization.

In some embodiments, the liquid overcoat composition 25 can includeconductive particulates that can be used to form randomly arrangedconductive pathways through the overcoat layer ultimately formed bycuring from the liquid overcoat composition. In other embodiments,conductive or non-conductive particulates in the liquid overcoatcomposition 25 can be used to initiate or maintain destabilization ofthe liquid overcoat composition 25 so the liquid overcoat composition 25can more easily separate, flow off and withdraw from the patterned layer24 of the low surface energy material. In some embodiments, the liquidovercoat composition 25 is substantially free of particulate material,which in this application means that the liquid overcoat compositionincludes less than about 5% by weight of conductive or non-conductiveparticulates, or less than about 1% by weight of conductive ornon-conductive particulates, or less than about 0.5% by weight ofconductive or non-conductive particulates. In some embodiments, theliquid overcoat composition 25 is free of conductive or non-conductiveparticulates, which means that the liquid overcoat composition includesno particulate material.

Suitable liquid overcoat compositions include a polymer, and desirablyan optically clear polymer. Examples of suitable polymeric materialsinclude, but are not limited to: polyacrylics such as polymethacrylates,polyacrylates and polyacrylonitriles, polyvinyl alcohols, polyesters(e.g., polyethylene terephthalate (PET), polyester naphthalate (PEN),and polycarbonates (PC)), polymers with a high degree of aromaticitysuch as phenolics or cresol-formaldehyde (Novolacs®), polystyrenes,polyvinyltoluene, polyvinylxylene, polyimides, polyamides,polyamideimides, polyetherimides, polysulfides, polysulfones,polyphenylenes, and polyphenyl ethers, polyurethane (PU), epoxy,polyolefins (e.g. polypropylene, polymethylpentene, and cyclic olefins),acrylonitrile-butadiene-styrene copolymer (ABS), cellulosics, siliconesand other silicon-containing polymers (e.g. polysilsesquioxanes andpolysilanes), polyvinylchloride (PVC), polyacetates, polynorbomenes,synthetic rubbers (e.g. EPR, SBR, EPDM), and fluoropolymers (e.g.,polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) orpolyhexafluoropropylene), copolymers of fluoro-olefin and hydrocarbonolefin (e.g., Lumiflon®), and amorphous fluorocarbon polymers orcopolymers (e.g., CYTOP® by Asahi Glass Co., or Teflon® AF by DuPontCorp.).

In other embodiments, the liquid overcoat composition 25 includes aprepolymer. A “prepolymer” refers to a mixture of monomers or a mixtureof oligomers or partial polymers that can polymerize and/or crosslink toform the polymeric matrix, as described herein. It is within theknowledge of one skilled in the art to select, in view of a desirablepolymeric matrix, a suitable monomer or partial polymer.

In some embodiments, the prepolymer is photo-curable, i.e., theprepolymer polymerizes and/or cross-links upon exposure to irradiationsuch as, for example ultraviolet (UV) radiation.

The liquid overcoat composition 25 may optionally include a solvent(e.g., during application). Any non-corrosive solvent that caneffectively solvate or disperse the polymeric overcoat material can beused, and examples include water, an alcohol, a ketone, an ether,tetrahydrofuran, hydrocarbons (e.g. cyclohexane) or an aromatic solvent(benzene, toluene, xylene, etc.). The solvent can be volatile, having aboiling point of no more than 200° C., no more than 150° C., or no morethan 100° C.

In some embodiments, the liquid overcoat composition 25 may include across-linker, a polymerization initiator, stabilizers (including, forexample, antioxidants, and UV stabilizers for longer product lifetimeand polymerization inhibitors for greater shelf-life), surfactants andthe like. In some embodiments, the liquid overcoat composition 25 mayfurther include a corrosion inhibitor. In some embodiments, the liquidovercoat composition 25 is conductive, and can include a conductivepolymer such as, for example, polyanilines, polythiophenes, andpolydiacetylenes.

In some embodiments, the liquid overcoat composition 25 can be cured ordried to form an optically clear material. A material is consideredoptically clear if the light transmission of the material is at least80% in the visible region (400 nm-700 nm). Unless specified otherwise,all the layers (including the substrate) described herein are preferablyoptically clear. The optical clarity of the liquid overcoat composition25 is typically determined by a multitude of factors, including withoutlimitation: the refractive index (RI), thickness, smoothness,consistency of the RI throughout the thickness, surface (includinginterface) reflection, and scattering caused by surface roughness and/orembedded particles.

In some embodiments, the liquid overcoat composition 25 includes an inksuch as those available under the trade designation FLEXOCURE FORCE fromFlint Group, Plymouth, Minn., as well as transparent varnishes fromNazdar (OP series), SolarFlex or SunBar series from Sun Chemical, andacrylate resins from Sartomer.

Referring now to FIG. 1C, the difference between the wettability of thepatterned low surface energy layer 24 and the wettability of theconductive surface 23 causes instability in the liquid overcoatcomposition 25. This instability causes the liquid overcoat composition25 to separate, then run off and withdraw from the patterned layer oflow surface energy material 24. The liquid overcoat composition 25 thenflows away from the patterned layer of low surface energy material 24and a first amount of the liquid overcoat composition 25 is directed tocollect in a discrete areas of the second region 52 of the conductivesurface 23, which are referred to herein as the first portion 54 of thesecond region 52. The presence of the low surface energy material in thepatterned layer 24 also causes the liquid overcoat composition 25 topull away and substantially uniformly recede from the edges 24A of thepatterned layer 24, leaving a second residual amount of the liquidovercoat composition 25 in a second portion 56 of the second region 52of the conductive surface 23 adjacent the edges 24A. The second residualamount of the liquid overcoat composition 25 overlying the secondportion 56 of the second region 52 of the conductive surface 23 is lessthan the first amount of the overcoat composition overlying the firstportion 54 of the second region 52 of the conductive surface 23. In theembodiment shown in FIG. 1C, none of the liquid overcoat compositionremains in the second portion 56 of the second region 52 of theconductive surface 23. In the embodiment of FIG. 1C the second portion56 is free of and uncovered by the liquid overcoat composition 25, whichleaves the conductive surface 23 completely exposed.

In another embodiment shown in FIG. 1C-1, a first amount of the liquidovercoat composition 27 does not completely recede from the secondportion 56 of the second region 52 of the conductive surface 23. Asecond residual amount 29 of the liquid overcoat composition 25 clingsto the edges 24A of the patterned layer 24 and overlies the secondportion 56 of the conductive surface 23. The thickness of the secondresidual amount 29 on the conductive surface 23 in the second portion 56can vary widely depending on the relative wettability of the patternedlayer 24 and the liquid overcoat composition 25, but in variousembodiments the thickness of the second residual amount 29 of the liquidovercoat composition 25 is no greater than about 250 nm.

Referring now to FIG. 1D, the liquid overcoat composition is curedand/or hardened into a protective layer 25A in the first portion 54 ofthe second region 52 of the conductive surface 23 of the conductivelayer 22. “Cure or curing” refers to a process where monomers or partialpolymers (e.g. oligomers comprising fewer than 150 monomer units)polymerize so as to form a solid polymeric matrix, or where polymerscross-link. Suitable polymerization or cross-linking conditions are wellknown in the art and include by way of example, heating the monomer,irradiating the monomer with visible or ultraviolet (UV) light, electronbeams, and the like. Alternatively, “harden(s) or hardening” may becaused by solvent removal during drying of a resist matrix material, forexample without polymerization or cross-linking.

Following curing, in the embodiment of FIG. 1D the second portion 56 ofthe second region 52 of the conductive surface 23 remains uncovered bythe protective layer 25A. This zone adjacent to the edges of thepatterned layer 24 having no residual amount of the protective layer 25Ain the second portion 56 effectively forms an arrangement of vias oraccess channels 60 that extend from above the protective layer 25A tothe conductive surface 23 of the conductive layer 22. In anotherembodiment not shown in FIG. 1D, a very thin residual amount of theprotective layer 25A with a thickness no greater than about 250 nm, orno greater than about 100 nm, or no greater than about 75 nm, or nogreater than about 50 nm, or no greater than about 10 nm, or no greaterthan about 5 nm, remains in the second portion 56 of the second region52 of the conductive surface 23. This extremely thin portion of theprotective layer 25A overlying the second portion 56 of the conductivesurface 23 forms an arrangement of vias or access channels 60 thatextend from above the protective layer 25A to the conductive surface 23of the conductive layer 22.

Referring to FIG. 1E, a layer of an electrically conductive material 30can be applied over the patterned low surface energy layer 24. Theconductive material 30 extends into the vias 60 and to the selectedareas of the conductive surface 23 of the conductive layer 22. In theembodiment of FIG. 1E, there electrically conductive material 30directly contacts the conductive surface 23 of the conductive layer 22.However, if a very thin residual amount of the protective layer 25A witha thickness no greater than about 250 nm, or no greater than about 100nm, or no greater than about 75 nm, or no greater than about 50 nm, orno greater than about 10 nm, or no greater than about 5 nm, remains inthe second portion 56 of the second region 52 of the conductive surface23, the conductive material 30 can rest on top of the protective layer25A and still form an electrical connection through the protective layer25A to the conductive surface 23 of the conductive layer 22.

In some embodiments, the conductive material 30 is a paste or adhesivematrix 32 having therein metal particles or scrim 34 of silver, gold,copper, aluminum and the like, and mixtures thereof. In otherembodiments, the particles 34 are nonconductive particles (for example,polymers) having a conductive coating. In various embodiments, thematrix 32 is selected from an acrylate adhesive, an epoxy adhesive, asilicone adhesive, or a mixture or combination thereof. In one example,the conductive material 30 is a silver ink such as those available fromPChem Associates, Bensalem, Pa., under the trade designation PFI-722.

The metal particles 34 provide conductivity through the thickness of thematrix 32. This conductivity enables electrical connection between theconductive layer 22 and a contact pad of an electronic component (notshown in FIG. 1E) without inducing undesirable “shorts” between thecontact pads in either the conductive layer 22 or the electroniccomponent.

In another embodiment not shown in FIG. 1E, an electrical connectioncould be made to the conductive layer 22 through the vias 60 by directlybonding the metal contacts of an electrical component to the conductivelayer 22. This direct bonding mitigates the need for any otherintermediate conductive paste or printed conductor between the metalcontacts of the electronic component and the conductive layer 22, whichcan simplify the construction of the electronic assembly. The electroniccomponent may vary widely depending on the intended application, and insome embodiments includes a flexible circuit, a printed circuit board(PCB), a glass panel, or a pattern of wires.

In some embodiments, multiple layers can be overcoated simultaneously(not shown in FIG. 1E), and the original via structure is maintained,thus allowing perfect registration of all the layers with the patternedlayer of the low energy material 24. The structure of the vias 60 allowselectrical connection to the conductive layer 22 even if multiple layersare applied.

Referring to another embodiment of the process illustrated schematicallyin FIG. 2A, a conductive layer 122 is disposed on a flexible substrate120. The flexible substrate 120 can be clear or opaque, conductive ornon-conductive (insulative), and suitable flexible substrates can beselected from any material that can be rolled up and processed in aroll-to-roll manufacturing process. Examples of suitable flexiblesubstrates 120 include, but are not limited to: polyesters (e.g.,polyethylene terephthalate (PET), polyester naphthalate (PEN), andpolycarbonate (PC)), polyolefins (e.g., linear, branched, and cyclicpolyolefins), polyvinyls (e.g., polyvinyl chloride, polyvinylidenechloride, polyvinyl acetals, polystyrene, polyacrylates, and the like),cellulose ester bases (e.g., cellulose triacetate, cellulose acetate),polysulphones such as polyethersulphone, polyimides, silicones and otherconventional polymeric films. Additional examples of suitable substratescan be found in, e.g., U.S. Pat. No. 6,975,067.

Optionally, a major surface 121 of the substrate 120 underlying theconductive layer 122 can be pre-treated to prepare the surface to betterreceive the subsequent deposition of the conductive layer. In someembodiments, the pre-treatment step can be carried out in conjunctionwith a patterning step to create patterned deposition of the conductivelayer 122. For example, pre-treatments can include solvent or chemicalwashing, heating, deposition of an optional patterned intermediatelayer, as well as further surface treatments such as plasma treatment,ultraviolet radiation (UV)-ozone treatment, or corona discharge.

The conductive layer 122 can be applied to the substrate 120 at a giventhickness selected to achieve desired optical and electrical properties.This application can be performed using known coating methods, such as,for example, slot coating, roll coating, Mayer rod coating, dip coating,curtain coating, slide coating, knife coating, gravure coating, notchbar coating or spraying, yielding a conductive nanowire layer on thesubstrate. The conductive layer 122 can also be depositednon-continuously using a printing technique including, but not limitedto, gravure, flexographic, screen, letterpress, ink-jet printing, andthe like.

Suitable materials for the conductive layer 122 include, but are notlimited to, layers of metals or metal alloys of Cu, Ag, Au and the like,indium tin oxide (ITO), or layers of conductive metal or non-metallicfilaments, fibers, rods, strings, strands, whiskers, or ribbons in asuitable binder. Examples of non-metallic conductive materials for theconductive layer 122 include, but are not limited to, carbon nanotubes(CNTs), metal oxides (e.g., vanadium pentoxide), metalloids (e.g.,silicon), conductive polymer fibers, and the like.

The conductive layer 122 is substantially continuous over at least aportion of the first major surface 121 of the flexible substrate 120,and desirably over at least 50%, 60%, 70%, 80%, or 90% of the area ofthe first major surface 121. The conductive layer 122 may be coatedcontinuously along the surface 121 of the flexible substrate 120, or maybe applied in discrete blocks or rectangles, leaving uncoated substrateareas between them, with the blocks or rectangles having a size similarto the overall size of the intended touch sensor being produced. By“substantially continuous” it is meant the conductive layer 122 isapplied at a sufficient density to render the surface 121 of thesubstrate 122 conductive, it being recognized that the surface 121 mayinclude individual conductive areas with relatively non-conductiveopenings or spaces between them.

Referring again to FIG. 2A, a patterned layer of an electricallyconductive material 130 is applied over a first region 150 of aconductive surface 123 of the conductive layer 122, leaving a secondregion 152 of the conductive surface 123 uncovered. In some embodiments,the conductive material 130 is a paste or adhesive matrix 132 havingtherein metal particles or scrim 134 of silver, gold, copper, aluminumand the like, and mixtures thereof. In other embodiments, the particles134 are nonconductive particles (for example, polymers) having aconductive coating. In various embodiments, the matrix 132 is selectedfrom an acrylate adhesive, an epoxy adhesive, a silicone adhesive, or amixture or combination thereof. In one example, the conductive material130 is a silver ink such as those available from PChem Associates,Bensalem, Pa., under the trade designation PFI-722.

The metal particles 134 provide conductivity through the thickness ofthe matrix 132, which enables electrical connection to the conductivelayer 122.

Referring now to FIG. 2B, a pattern 124 of a low surface energy materialis coated on and overlies a first portion 151 of the patterned layer ofelectrically conductive material 130, which leaves a second portion 153of the patterned layer of electrically conductive material 130uncovered. In various embodiments, the pattern 124 of the low surfaceenergy material is printed in registration with the pattern of theelectrically conductive material 130 using alignment techniques such as,for example, edge detection or tracking printed fiducial marks.

As above, the term low surface energy material refers to any material(for example, an ink) that can induce dewetting of a subsequentlyapplied overcoat composition in a desired area of the surface 123 of theconductive layer 122.

Suitable low surface energy materials for the pattern 124 can varywidely, and can include, but are not limited to plastics, rubbers andcomposite materials with a surface energy of less than about 100 mJ/m²,less than about 50 mJ/m², less than about 30 mJ/m², less than about 20mJ/m² or less than about 10 mJ/m². Non-limiting examples of low surfaceenergy materials include fluoropolymers such as polyhexafluoropropylene,polytetrafluoroethylene (PTFE) and the like, was well as polymericresins such as poly(vinylidene fluoride) (PVF), polyethylene (PE),polypropylene (PP), poly(methylmethacrylate) (PMMA), polystyrene (PS),polyamides, poly(vinylchloride) (PVC), poly(vinylidene chloride),poly(ethylene terephthalate) (PET), epoxies, phenol resins,styrene-butadiene rubber, acrylonitrile rubbers, and the like, thermallycurable or ultraviolet (UV) curable silicones, and mixtures andcombinations thereof. In some embodiments, the low surface energymaterial included silicones such as those available from Dow Chemical,Midland, Mich., under the trade designation Syl-Off.

The coating composition used to form the pattern 124 typically includesat least one of the low surface energy materials listed above andoptional additives such as a fluorinated or non-fluorinated surfactant,a crosslinker, an aqueous or organic solvent, and the like. In someexample embodiments, the coating solution used to form the pattern 124includes a low surface energy material such as a thermally or UV curablesilicone “ink” and a crosslinker, or an acrylic resin and a fluorinatedsurfactant. In some embodiments, the coating composition used to formthe pattern 124 may be combined with a conductive material such as, forexample, metal particles or a silver paste ink, to make the pattern 124of the low surface energy material itself be conductive.

The coating composition used to form the pattern 124 may be coated onthe patterned layer 130 of electrically conductive material by a widevariety of printing techniques such as, for example, flexographicprinting, gravure coating, offset printing, screen printing, plasmadeposition, photolithography, micro-contact printing, inkjet printing orselective removal of a uniform layer of the material by laser or otheretching technique, optically writing with light or a laser,electrostatic spray or by plasma treatment.

In various embodiments, the patterned layer 124 of the low energymaterial has a dry thickness of about 100 nm to about 10 μm.

Referring now to FIG. 2C, a liquid overcoat composition 125 is coatedover the conductive surface 123 of the conductive layer 122, andinitially covers both the printed pattern of the low surface energymaterial 124 and the patterned layer of the electrically conductivematerial 130, as well as the second region 152 of the surface 123 thatis uncoated with the patterns of the low surface energy material 124 orthe patterned layer of the electrically conductive material 130.

In various embodiments, the liquid overcoat composition 125 is coated toa thickness of about 10 μm to about 15 μm. The liquid overcoatcomposition 125 may be applied to the conductive surface 123 using anysuitable printing technique including, for example, flood coating,gravure coating, curtain coating, bead coating, offset printing, screenprinting, inkjet printing, spraying, or by means of a blade, roller, orair knife.

The liquid overcoat composition 125 can include any material having asurface energy sufficiently greater than that of the low surface energymaterial in the pattern 124 to cause the liquid overcoat composition todewet from the pattern 124 in a commercially useful amount of time. Thespeed at which the liquid overcoat composition 125 rearranges about thepatterned layer 124 can impact the speed at which the predeterminedareas of the conductive surface 123 can be coated in a roll-to-rollprocess. A discussion of the rates of recession of liquids from lowsurface energy materials can be found in, for example, Brouchard-Wyartand de Gennes, Advan. Colloid Interface Sci., 39 (1992), which isincorporated herein by reference.

If the liquid coating composition 125 is coated as a uniform layer, itis necessary to destabilize the layer so the liquid overcoat compositionseparates, flows off, and withdraws from the patterned layer 124 of thelow surface energy material. If the liquid overcoat composition issufficiently dilute, or when it becomes sufficiently thin duringsubsequent drying steps, spontaneous dewetting from the pattern 124 tothe regions 152 of the conductive surface 123 areas takes place, withoutthe need for any active destabilization.

In some embodiments, the liquid overcoat composition 125 can includeconductive particulates that can be used to form randomly arrangedconductive pathways through the overcoat layer ultimately formed bycuring from the liquid overcoat composition. In other embodiments,conductive or non-conductive particulates in the liquid overcoatcomposition 125 can be used to initiate or maintain destabilization ofthe liquid overcoat composition 125 so the liquid overcoat composition125 can more easily separate, flow off and withdraw from the patternedlayer 124 of the low surface energy material and the patterned layer ofelectrically conductive material 130. In some embodiments, the liquidovercoat composition 125 is substantially free of particulate material,which in this application means that the liquid overcoat compositionincludes less than about 5% by weight of conductive or non-conductiveparticulates, or less than about 1% by weight of conductive ornon-conductive particulates, or less than about 0.5% by weight ofconductive or non-conductive particulates. In some embodiments, theliquid overcoat composition 125 is free of conductive or non-conductiveparticulates, which means that the liquid overcoat composition includesno particulate material.

Suitable liquid overcoat compositions include a polymer, and desirablyan optically clear polymer. Examples of suitable polymeric materialsinclude, but are not limited to: polyacrylics such as polymethacrylates,polyacrylates and polyacrylonitriles, polyvinyl alcohols, polyesters(e.g., polyethylene terephthalate (PET), polyester naphthalate (PEN),and polycarbonates (PC)), polymers with a high degree of aromaticitysuch as phenolics or cresol-formaldehyde (Novolacs®), polystyrenes,polyvinyltoluene, polyvinylxylene, polyimides, polyamides,polyamideimides, polyetherimides, polysulfides, polysulfones,polyphenylenes, and polyphenyl ethers, polyurethane (PU), epoxy,polyolefins (e.g. polypropylene, polymethylpentene, and cyclic olefins),acrylonitrile-butadiene-styrene copolymer (ABS), cellulosics, siliconesand other silicon-containing polymers (e.g. polysilsesquioxanes andpolysilanes), polyvinylchloride (PVC), polyacetates, polynorbomenes,synthetic rubbers (e.g. EPR, SBR, EPDM), and fluoropolymers (e.g.,polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) orpolyhexafluoropropylene), copolymers of fluoro-olefin and hydrocarbonolefin (e.g., Lumiflon®), and amorphous fluorocarbon polymers orcopolymers (e.g., CYTOP® by Asahi Glass Co., or Teflon® AF by DuPontCorp.).

In other embodiments, the liquid overcoat composition 125 includes aprepolymer. A “prepolymer” refers to a mixture of monomers or a mixtureof oligomers or partial polymers that can polymerize and/or crosslink toform the polymeric matrix, as described herein. It is within theknowledge of one skilled in the art to select, in view of a desirablepolymeric matrix, a suitable monomer or partial polymer.

In some embodiments, the prepolymer is photo-curable, i.e., theprepolymer polymerizes and/or cross-links upon exposure to irradiationsuch as, for example ultraviolet (UV) radiation.

The liquid overcoat composition 125 may optionally include a solvent(e.g., during application). Any non-corrosive solvent that caneffectively solvate or disperse the polymeric overcoat material can beused, and examples include water, an alcohol, a ketone, an ether,tetrahydrofuran, hydrocarbons (e.g. cyclohexane) or an aromatic solvent(benzene, toluene, xylene, etc.). The solvent can be volatile, having aboiling point of no more than 200° C., no more than 150° C., or no morethan 100° C.

In some embodiments, the liquid overcoat composition 125 may include across-linker, a polymerization initiator, stabilizers (including, forexample, antioxidants, and UV stabilizers for longer product lifetimeand polymerization inhibitors for greater shelf-life), surfactants andthe like. In some embodiments, the liquid overcoat composition 125 mayfurther include a corrosion inhibitor. In some embodiments, the liquidovercoat composition 125 is conductive, and can include a conductivepolymer such as, for example, polyanilines, polythiophenes, andpolydiacetylenes.

In some embodiments, the liquid overcoat composition 125 can be cured ordried to form an optically clear material. A material is consideredoptically clear if the light transmission of the material is at least80% in the visible region (400 nm-700 nm). Unless specified otherwise,all the layers (including the substrate) described herein are preferablyoptically clear. The optical clarity of the liquid overcoat composition125 is typically determined by a multitude of factors, including withoutlimitation: the refractive index (RI), thickness, smoothness,consistency of the RI throughout the thickness, surface (includinginterface) reflection, and scattering caused by surface roughness and/orembedded particles.

In some embodiments, the liquid overcoat composition 125 includes an inksuch as those available under the trade designation FLEXOCURE FORCE fromFlint Group, Plymouth, Minn.

Referring now to FIG. 2D, the difference between the wettability of thepatterned low surface energy layer 124 and the wettability of theconductive surface 123 and the patterned layer of electricallyconductive material 130 causes instability in the liquid overcoatcomposition 125. This instability causes the liquid overcoat composition125 to separate, then run off and withdraw from the patterned lowsurface energy layer 124. The liquid overcoat composition 125 then flowsaway from the patterned low surface energy layer 124 and the patternedlayer of electrically conductive material 130. A first amount of theliquid overcoat composition then collects in discrete areas of thesecond region 152 of the conductive surface 123. The presence of the lowsurface energy material in the patterned layer 124 also causes theliquid overcoat composition 125 to pull away and recede from the edges124A of the patterned layer of low surface energy material 124, leavinga second residual amount of the liquid overcoat composition 125 in thesecond portion 153 of the patterned layer of electrically conductivematerial 130 adjacent to the edges 124A.

The second residual amount of the liquid overcoat composition 125overlying the second portion 153 of the patterned layer of electricallyconductive material 130 is less than the first amount of the liquidovercoat composition 125 overlying the second region 152 of theconductive surface 123. In the embodiment shown in FIG. 2C, none of theliquid overcoat composition 125 remains in the second portion 153. Inthe embodiment of FIG. 2D the second portion 153 is free of anduncovered by the liquid overcoat composition 125, which leaves thepatterned layer 130 of conductive material completely exposed.

In another embodiment not shown in FIG. 2D, a first amount of the liquidovercoat composition 125 does not completely recede from the secondportion 153 of the patterned layer of conductive material 130. A secondresidual amount of the liquid overcoat composition 125 clings to theedges 124A of the patterned layer 124 and overlies the second portion153. The thickness of the second residual amount on the second portion153 of the patterned conductive layer 130 can vary widely depending onthe relative wettability of the patterned layer 124 and the liquidovercoat composition 125, but in various embodiments the thickness ofthe second residual amount of the liquid overcoat composition 125overlying the second portion 153 of the patterned conductive layer 130is no greater than about 250 nm.

Referring now to FIG. 2E, the liquid overcoat composition is curedand/or hardened into a protective layer 125A in the first region 152 ofthe conductive surface 123 of the conductive layer 122. “Cure or curing”refers to a process where monomers or partial polymers (e.g. oligomerscomprising fewer than 150 monomer units) polymerize so as to form asolid polymeric matrix, or where polymers cross-link. Suitablepolymerization or cross-linking conditions are well known in the art andinclude by way of example, heating the monomer, irradiating the monomerwith visible or ultraviolet (UV) light, electron beams, and the like.Alternatively, “harden(s) or hardening” may be caused by solvent removalduring drying of a resist matrix material, for example withoutpolymerization or cross-linking.

Following cure, the second portion 153 of the patterned layer 130 ofelectrically conductive material remains uncovered by the protectivelayer 125A. This zone having no residual amount of the protective layer125A effectively forms an arrangement of vias or access channels 160that extend from above the protective layer 125A to the conductivesurface 123 of the conductive layer 122. In another embodiment not shownin FIG. 2E, a very thin residual amount of the protective layer 125Awith a thickness no greater than about 250 nm, or no greater than about100 nm, or no greater than about 75 nm, or no greater than about 50 nm,or no greater than about 10 nm, or no greater than about 5 nm, remainsin the second portion 153 of the patterned layer of conductive material130. This extremely thin portion of the protective layer 25A overlyingthe second portion 153 forms an arrangement of vias or access channels160 that extend from above the protective layer 125A to the surface 153of the patterned layer of conductive material 130.

As in FIG. 1E above (not shown in FIG. 2E), a layer of an electricallyconductive material can be applied in the vias 160 to provide electricalconnection to selected areas of the conductive surface 123 of theconductive layer 122. However, if a very thin residual amount of theprotective layer 125A with a thickness no greater than about 250 nm, orno greater than about 100 nm, or no greater than about 75 nm, or nogreater than about 50 nm, or no greater than about 10 nm, or no greaterthan about 5 nm, remains in the second portion 153 of the patternedlayer of conductive material 130, the conductive material can rest ontop of the protective layer 125A and still form an electrical connectionthrough the protective layer 125A to the conductive surface 153 of thepatterned layer of conductive material 130 and to the conductive layer122.

In another embodiment not shown in FIG. 2E, an electrical connectioncould be made to the conductive layer 122 through the vias 160 bydirectly bonding the metal contacts of an electrical component to theconductive layer 122. The electronic component may vary widely dependingon the intended application, and in some embodiments includes a flexiblecircuit, a printed circuit board (PCB), a glass panel, or a pattern ofwires.

As above, using the process of FIGS. 2A-2E, multiple layers can beovercoated simultaneously, and the layer structure is maintained, thusallowing perfect registration of all the layers with the patterned lowenergy layer 124, and further maintaining the structure of the vias 160,which allows electrical connection to the conductive layer 122.

Referring to FIG. 3, an example of a touch-screen assembly 200 includesa LCD layer 272 adjacent to a layer of glass 214, which provides asubstrate for an electronic assembly construction 270 made using theprocesses described above. The electronic assembly construction 270includes a conductive layer 216, which is electrically connected toflexible circuits 260 via a conductive adhesive layer 250. Electricaltraces 280 on the flexible circuits 260 connect the assembly 200 tocomponents of a display device such as a computer, mobile phone, tablet,and the like. A flexible transparent surface 276 overlying theelectronic assembly construction 270 provides a point of interactionwith a user of the display device.

The processes of this disclosure will now be further described in thefollowing non-limiting examples.

EXAMPLES Example 1

A 50 Ohm/Sq. silver nanowire coating was prepared as described inExample 1 of WO2014088950 A1. This film was used as input to aroll-to-roll flexographic process, and a variety of patterns wereprinted onto the nanowire-coated side of the film, using a lowsurface-energy ink.

The first ink was composed of a mixture of 97.5% by weight Dow Syl-Off7170 silicone and 2.5% by weight 7488 crosslinker. The Syl-Off siliconewas printed at a speed of 5 meters/min using a 1.0 BCM/in² aniloxprinting roll. The Syl-off silicone was thermally cured by running itthrough an oven heated to 120° C. for approximately 45-60 seconds.

A second UV-curable silicone ink was printed at a speed of 5 meters/minusing the 1.0 BCM/in² anilox printing roll. The UV curable silicone inkwas passed through a Fusion UV Curing system equipped with an H-Bulblight source for curing.

The silicone-printed substrate was then over-coated with a mixture of25% by weight Flint Group FC Force printing ink (Product Code:UFR0-0061-465U) in 75% by glycol ether PM, using a #5 Meyer rod,targeting an approximate 10-15 μm wet film coating (or roughly, a 2-4 μmdry-film coating).

The polymer-solvent coating was dried for 1 minute in an oven set to 80°C., and then cured using a Fusion UV System equipped with a H-bulb UVsource.

Immediately upon coating the polymer-solvent mixture (i.e. less thanabout 1-5 seconds), it dewet from the low surface-energy siliconeprinted features, leaving openings to the underlying silver nanowirecoating. FIG. 4A shows a regular array of 500 μm pitch lines 302 thatwas printed on a 50 Ohm/Sq. silver nanowire coating on Dupont ST-504PET, with corresponding dewetted over-coat layers 304. FIG. 4Bdemonstrates a second printed pattern 402, which represents the openingof a contact pad (e.g. the contact pad of a silver interconnectpattern), for which the square opening is approximately 2 mm on eachside, and a corresponding de-wetted over-coating layer 404.

PChem PFI-722 silver nanoparticle ink was applied with a small brush ontop of the patterned polymer layer and underlying (and exposed) silvernanowire layer to make contact between the PChem silver pad and theunderlying nanowire layer. Contact between the Pchem ink and silvernanowire substrate was determined with a volt-meter (i.e. a Fluke meterused to measure electrical resistance). FIG. 5A shows a regular array of500 μm pitch lines 502 near a silver contact pad 503 with the PChemPFI-722 silver ink pasted on top of the pattern over-coat layer 504. Asseen clearly in FIG. 5B, the PChem silver makes contact with theunderlying nanowire layer 505 in contact zones 507 in the gaps betweenthe dewetted over-coating layer and the low surface-energy siliconeprint features.

Example 2

A 50 Ohm/Sq. silver nanowire coating was prepared as described inExample 1 from WO2014088950 A1. A conductive silver interconnect patternwas then printed on top of the silver nanowire substrate with a desktopflexographic printing unit, using a 0.067 DPR flexographic stamp and a10 bcm/in² anilox roll. The conductive silver ink was purchased fromInkTek (Product Designation: TEC-PR-010). The printed sample was driedand cured in an oven set 120° C. for 3-5 minutes, and then removed fromthe oven to cool.

A silicon ink (97.5% Syl-Off 7170 with 2.5% crosslinker) was then wipedonto the surface of the printed silver interconnect pads with a smallQ-tip applicator, leaving a very thin coating. The sample was thenplaced in an oven set to 120° C. for 1-2 minutes to cure the siliconecoating.

The substrate was then over-coated with a mixture of 25% by weight FlintGroup FC Force printing ink (Product Code: UFR0-0061-465U) in 75% byglycol ether PM, using a #5 Meyer rod, so as to target an approximate10-15 μm wet film coating (or roughly, a 2-4 μm dry-film coating).

The polymer-solvent coating was dried for 1 minute in an oven set to 80°C., and then cured using a Fusion UV System equipped with a H-bulb UVsource.

Referring to FIG. 6, immediately upon coating the polymer-solventmixture (i.e. <1-5 seconds), it dewet into overcoat areas 604 from thelow surface-energy silicone printed features 602, leaving openings tothe underlying silver interconnect pad.

Electrical contact to the underlying silver nanowire was confirmed witha Fluke volt-meter, testing between opened interconnect pads.

Embodiment 1

A composite article, comprising:

a conductive layer on at least a portion of a flexible substrate,wherein the conductive layer comprises a conductive surface;

a patterned layer on a first region of the conductive surface, whereinthe patterned layer comprises a low surface energy material;

an overcoat layer on a first portion of a second region of theconductive surface unoccupied by the patterned layer, wherein theovercoat layer is free of conductive particulates;

a via in a second portion of the second region of the conductive surfacebetween an edge of the patterned layer of the low surface energymaterial and the overcoat layer; and

a conductive material in the via, wherein the conductive materialprovides an electrical connection to the conductive surface.

Embodiment 2

The composite article according to Embodiment 1, wherein the via isuncovered by the overcoat layer.

Embodiment 3

The composite article according to Embodiment 1, wherein the via iscovered by the overcoat layer, and wherein the overcoat layer in the viahas a thickness of no more than about 250 nm.

Embodiment 4

The composite article according to Embodiment 1, wherein the via iscovered by the overcoat layer, and wherein the overcoat layer in the viahas a thickness of no more than about 100 nm.

Embodiment 5

The composite article according to any of Embodiments 1 to 4, whereinthe substrate is an optical element.

Embodiment 6

The composite article according to any of Embodiments 1 to 5, whereinthe conductive material is selected from conductive adhesives,conductive pastes, and solder.

Embodiment 7

A composite article, comprising:

a conductive layer on at least a portion of a flexible substrate,wherein the conductive layer comprises a conductive surface;

a patterned conductive layer on a first region of the conductivesurface, wherein a second region of the conductive surface is uncoveredby the patterned conductive layer;

a patterned low surface energy layer on a first portion of the patternedconductive layer, wherein a second portion of the patterned conductivelayer is uncovered by the patterned low surface energy layer;

an overcoat layer on the second region of the conductive surface,wherein the overcoat layer is free of conductive particulates;

a via between the overcoat layer and first portion of the patternedconductive layer, wherein the via overlies the second portion of thepatterned conductive; and

a conductive material in the via, wherein the conductive materialprovides an electrical connection to the patterned conductive layer andthe conductive surface.

Embodiment 8

The composite article according to Embodiment 7, wherein the via isuncovered by the overcoat layer.

Embodiment 9

The composite article according to Embodiment 7, wherein the via iscovered by the overcoat layer, and wherein the overcoat layer in the viahas a thickness of no more than about 250 nm.

Embodiment 10

The composite article according to Embodiment 7, wherein the via iscovered by the overcoat layer, and wherein the overcoat layer in the viahas a thickness of no more than about 100 nm.

Embodiment 11

The composite article according to any of Embodiments 7 to 10, whereinthe substrate is an optical element.

Embodiment 12

The composite article according to any of Embodiments 7 to 11, whereinthe conductive material is selected from conductive adhesives,conductive pastes, and solder.

Embodiment 13

A touch screen display comprising:

a liquid crystal display;

a composite article according to any of claims 1 to 12; and

a flexible transparent surface overlying the electronic assembly.

Embodiment 14

A method of forming a composite article, comprising:

coating a patterned layer comprising a low surface energy material ontoa first region of a conductive surface disposed on a flexible substrate,wherein a second region of the conductive surface remains uncovered bythe patterned layer;

coating a layer of a liquid overcoat composition over the patternedlayer of the low energy material and the second regions of theconductive surface, wherein the liquid overcoat composition has asurface energy different from the surface energy of the low surfaceenergy material;

de-wetting the liquid overcoat composition from the patterned layer ofthe low surface energy material such that the liquid overcoatcomposition withdraws from the patterned layer of the low surface energymaterial and a first amount of the liquid overcoat composition collectsin a first portion of the second region of the conductive surface,wherein the liquid overcoat composition recedes from an edge of thepatterned layer of the low surface energy material such that a secondresidual amount of the liquid overcoat composition less than the firstamount remains in a second portion of the second region of theconductive surface adjacent to the edge of the patterned layer of thelow surface energy material;

curing the liquid overcoat composition to form a discontinuous overcoatlayer in the first portion of the second region of the conductivesurface and a via in the second portion of the second region of theconductive surface, wherein the via is adjacent to the edge of thepatterned layer of the low surface energy material; and

electrically contacting the conductive surface through the via.

Embodiment 15

The method according to Embodiment 14, wherein the via is uncovered bythe overcoat layer.

Embodiment 16

The method according to Embodiment 14, wherein the via is covered by theovercoat layer, and wherein the overcoat layer in the via has athickness of no more than about 250 nm.

Embodiment 17

The method according to Embodiment 14, wherein the via is covered by theovercoat layer, and wherein the overcoat layer in the via has athickness of no more than about 100 nm.

Embodiment 18

The method according to Embodiment 14, wherein the overcoat layer isfree of electrically conductive particulates.

Embodiment 19

The method according to any of Embodiments 14 to 18, wherein thesubstrate comprises a polymeric film.

Embodiment 20

The method according to any of Embodiments 14 to 19, wherein thesubstrate is an optical element.

Embodiment 21

The method according to Embodiment 20, wherein the optical elementcomprises a multilayer optical film.

Embodiment 22

The method according to any of Embodiments 14 to 21, wherein the lowsurface energy material comprises a silicone or an acrylic.

Embodiment 23

The method according to Embodiments 22, wherein the low surface energymaterial comprises a thermally cured silicone or an ultraviolet (UV)cured silicone.

Embodiment 24

The method according to Embodiment 22, wherein the low surface energymaterial comprises an acrylic and a fluorinated surfactant.

Embodiment 25

The method according to any of Embodiments 14 to 24, wherein the lowsurface energy material is patterned by at least one of flexographicprinting, gravure printing, ink-jet printing, or screen printing.

Embodiment 26

The method according to any of Embodiments 14 to 25, wherein the lowsurface energy material is conductive.

Embodiment 27

The method according to any of Embodiments 14 to 26, wherein theelectrically contacting the conductive layer in the via comprisesapplying a conductive material in the via, wherein the conductivematerial is selected from conductive adhesives, conductive pastes,solder, and combinations thereof.

Embodiment 28

The method according to any of Embodiments 14 to 27, wherein theprotective overcoat composition comprises a UV-curable resin.

Embodiment 29

An electronic assembly made according to the method of any ofEmbodiments 14 to 28.

Embodiment 30

A method of forming a composite article, comprising:

coating a first patterned layer of a conductive material on a firstregion of a conductive surface on a conductive layer disposed on aflexible substrate, wherein a second region of the conductive surface isuncoated by the first patterned layer of the conductive material;

coating a second patterned layer of a low surface energy material on afirst portion of the first patterned layer of the conductive material,wherein a second portion of the first patterned layer is uncoated by thesecond patterned layer;

coating a layer of a liquid overcoat composition onto the first and thesecond regions of the conductive surface, wherein the liquid overcoatcomposition has a surface energy greater than the surface energy of thelow surface energy material in the second patterned layer;

de-wetting the liquid overcoat composition from the second patternedlayer of the low surface energy material such that a first amount of theliquid overcoat composition withdraws from the second patterned layerand collects in the second region of the conductive surface, and whereina second amount of the liquid overcoat composition less than the firstamount remains in the second portion of the first patterned layer of theconductive material;

curing the liquid overcoat composition to form a discontinuous overcoatlayer in the second region of the conductive surface, wherein theovercoat layer is separated from the second patterned layer by a viaoverlying the second portion of the first patterned layer; and

electrically contacting the second portion of the first patterned layerthrough the via.

Embodiment 31

The method according to Embodiment 30, wherein the via is uncovered bythe overcoat layer.

Embodiment 32

The method according to Embodiment 30, wherein the via is covered by theovercoat layer, and wherein the overcoat layer in the via has athickness of no more than about 250 nm.

Embodiment 33

The method according to Embodiment 30, wherein the via is covered by theovercoat layer, and wherein the overcoat layer in the via has athickness of no more than about 100 nm.

Embodiment 34

The method according to Embodiment 30, wherein the overcoat layer isfree of electrically conductive particulates.

Embodiment 35

The method according to any of Embodiments 30 to 34, wherein thesubstrate comprises a polymeric film.

Embodiment 36

The method according to any of Embodiments 30 to 35, wherein thesubstrate is an optical element.

Embodiment 37

The method according to Embodiment 36, wherein the optical elementcomprises a multilayer optical film.

Embodiment 38

The method according to any of Embodiments 30 to 37, wherein the lowsurface energy material comprises a silicone or an acrylic.

Embodiment 39

The method according to Embodiment 38, wherein the low surface energymaterial comprises a thermally cured silicone or an ultraviolet (UV)cured silicone.

Embodiment 40

The method according to Embodiment 38, wherein the low surface energymaterial comprises an acrylic and a fluorinated surfactant.

Embodiment 41

The method according to any of Embodiments 30 to 40, wherein the lowsurface energy material is patterned by at least one of flexographicprinting, gravure printing, ink-jet printing, or screen printing.

Embodiment 42

The method according to any of Embodiments 30 to 41, wherein the lowsurface energy material is conductive.

Embodiment 43

The method according to any of Embodiments 30 to 42, wherein theelectrically contacting the conductive layer in the via comprisesapplying a conductive material in the via, wherein the conductivematerial is selected from conductive adhesives, conductive pastes,solder, and combinations thereof.

Embodiment 44

The method according to any of Embodiments 30 to 43, wherein theprotective overcoat composition comprises a UV-curable resin.

Embodiment 45

An electronic assembly made according to the method of any ofEmbodiments 30 to 44.

Various embodiments of the invention have been described. These andother embodiments are within the scope of the following claims.

The invention claimed is:
 1. A composite article, comprising: aconductive layer on at least a portion of a flexible substrate, whereinthe conductive layer comprises a conductive surface; a patterned layeron a first region of the conductive surface, wherein the patterned layercomprises a low surface energy material; an overcoat layer on a firstportion of a second region of the conductive surface unoccupied by thepatterned layer, wherein the overcoat layer is free of conductiveparticulates; a via in a second portion of the second region of theconductive surface between an edge of the patterned layer of the lowsurface energy material and the overcoat layer, wherein the via iscovered by the overcoat layer, and wherein the overcoat layer in the viahas a thickness of no more than about 250 nm; and a conductive materialin the via, wherein the conductive material provides an electricalconnection to the conductive surface.
 2. The composite article accordingto claim 1, wherein the via is uncovered by the overcoat layer.
 3. Thecomposite article according to claim 1, wherein the substrate is anoptical element.
 4. The composite article according to claim 1, whereinthe conductive material is selected from conductive adhesives,conductive pastes, and solder.
 5. A composite article, comprising: aconductive layer on at least a portion of a flexible substrate, whereinthe conductive layer comprises a conductive surface; a patternedconductive layer on a first region of the conductive surface, wherein asecond region of the conductive surface is uncovered by the patternedconductive layer; a patterned low surface energy layer on a firstportion of the patterned conductive layer, wherein a second portion ofthe patterned conductive layer is uncovered by the patterned low surfaceenergy layer; an overcoat layer on the second region of the conductivesurface, wherein the overcoat layer is free of conductive particulates;a via between the overcoat layer and the first portion of the patternedconductive layer, wherein the via overlies the second portion of thepatterned conductive layer, wherein the via is covered by the overcoatlayer, and wherein the overcoat layer in the via has a thickness of nomore than about 250 nm; and a conductive material in the via, whereinthe conductive material provides an electrical connection to thepatterned conductive layer and the conductive surface.
 6. The compositearticle according to claim 5, wherein the substrate is an opticalelement.
 7. The composite article according to claim 5, wherein theconductive material is selected from conductive adhesives, conductivepastes, and solder.
 8. A method of forming a composite article,comprising: coating a patterned layer comprising a low surface energymaterial onto a first region of a conductive surface disposed on aflexible substrate, wherein a second region of the conductive surfaceremains uncovered by the patterned layer; coating a layer of a liquidovercoat composition over the patterned layer of the low energy materialand the second regions of the conductive surface, wherein the liquidovercoat composition has a surface energy different from the surfaceenergy of the low surface energy material; de-wetting the liquidovercoat composition from the patterned layer of the low surface energymaterial such that the liquid overcoat composition withdraws from thepatterned layer of the low surface energy material and a first amount ofthe liquid overcoat composition collects in a first portion of thesecond region of the conductive surface, wherein the liquid overcoatcomposition recedes from an edge of the patterned layer of the lowsurface energy material such that a second residual amount of the liquidovercoat composition less than the first amount remains in a secondportion of the second region of the conductive surface adjacent to theedge of the patterned layer of the low surface energy material; curingthe liquid overcoat composition to form a discontinuous overcoat layerin the first portion of the second region of the conductive surface anda via in the second portion of the second region of the conductivesurface, wherein the via is adjacent to the edge of the patterned layerof the low surface energy material, further wherein the via is coveredby the overcoat layer in the second portion of the second region of theconductive surface, and additionally wherein the overcoat layer in thevia has a thickness of no more than about 250 nm; and electricallycontacting the conductive surface through the via.
 9. The methodaccording to claim 8, wherein the overcoat layer is free of electricallyconductive particulates.
 10. A method of forming a composite article,comprising: coating a first patterned layer of a conductive material ona first region of a conductive surface on a conductive layer disposed ona flexible substrate, wherein a second region of the conductive surfaceis uncoated by the first patterned layer of the conductive material;coating a second patterned layer of a low surface energy material on afirst portion of the first patterned layer of the conductive material,wherein a second portion of the first patterned layer is uncoated by thesecond patterned layer; coating a layer of a liquid overcoat compositiononto the first and the second regions of the conductive surface, whereinthe liquid overcoat composition has a surface energy greater than thesurface energy of the low surface energy material in the secondpatterned layer; de-wetting the liquid overcoat composition from thesecond patterned layer of the low surface energy material such that afirst amount of the liquid overcoat composition withdraws from thesecond patterned layer and collects in the second region of theconductive surface, and wherein a second amount of the liquid overcoatcomposition less than the first amount remains in the second portion ofthe first patterned layer of the conductive material; curing the liquidovercoat composition to form a discontinuous overcoat layer in thesecond region of the conductive surface, wherein the overcoat layer isseparated from the second patterned layer by a via overlying the secondportion of the first patterned layer, further wherein the via is coveredby the overcoat layer in the second portion of the first patternedlayer, and additionally wherein the overcoat layer in the via has athickness of no more than about 250 nm; and electrically contacting thesecond portion of the first patterned layer through the via.
 11. Themethod according to claim 10, wherein the overcoat layer is free ofelectrically conductive particulates.